As for imaging techniques which make it possible to obtain a distance in a depth direction as two-dimensional array information, various methods such as a technique using reference light and a stereo distance measurement technique using a plurality of cameras are being studied. Especially in recent years, needs for comparatively inexpensive products functioning as new input devices in public welfare use have increased.
As a distance imaging scheme in which reference light is not used to reduce a system cost, there is a triangulation scheme utilizing the parallax. In this scheme, stereo cameras and compound eye cameras are known. In these cases, a plurality of cameras are used, and there is a problem such as a gigantic system and a failure rate increase due to an increase of the number of parts.
In a proposed structure, a microlens array having a plurality of microlenses is disposed in an upper part of a pixel and a plurality of pixels are disposed in a lower part of each microlens. According to this structure, it is possible to acquire an image group having parallax by taking a pixel block as a unit. Owing to this parallax, refocus processing or the like based on distance estimation of an object and distance information becomes possible.
Since the structure has a plurality of microlenses, however, there is a problem that initial correction is difficult when an error is caused in the position relation of a microlens image by an error or distortion in an optical system such as an attachment error of the microlens array or distortion of an image formation lens, and an error and picture quality degradation occur in the distance estimation and image reconstruction. Furthermore, since the optical system is an optical system which is used for imaging of both a two-dimensional image and a three-dimensional image and which has the microlens array incorporated therein, it is difficult to apply ordinary correction means as it is.